The present invention relates to an AC generator control apparatus for automobiles for switching the output voltage of an AC generator into any of plural variations according to an external signal having a variable duty ratio.
FIG. 3 shows the configuration of the conventional AC generator control apparatus for automobiles. This AC generator control apparatus for automobiles includes an AC generator 1 having a field coil 102 which is driven by a car engine (system) not shown and generates a rotating field, and an armature winding 101 generates an AC voltage through the generated rotating field and outputs the AC voltage; a rectifier 2 for rectifying the generated voltage of the AC generator 1 and providing the generated voltage to a battery 5 or an electric load 6 through a main output terminal 201; a voltage regulator 3 for controlling the exciting current of the field coil 102 depending on the charged voltage of the battery 5 or the rectified output voltage provided for the electric load 6, and for regulating the generated voltage of the AC generator 1; a load switch 7 for connecting the rectified voltage from the rectifier 2 or the charged voltage of the battery 5 to the electric load 6; and a key switch 8 transmitting an exciting current from the battery 5 to the field coil 102 through a charge indication lamp 9 when the system (engine) is started.
The rectifier 2 is provided with an auxiliary output terminal 202. The auxiliary output terminal 202 is connected to one end of the charge indication lamp 9. When the electric potential of the auxiliary output terminal 202 becomes equal to that of the charging terminal of the battery 5, the charge indication lamp 9 is turned off and the charging operation is started.
The voltage regulator 3 connects voltage dividing resistors 301, 302, and 303 serially connected between the charge detection terminal of the battery 5 and the ground through a lead wire C for use in detecting a charged voltage, and a transistor 320, whose collector and emitter are connected across the voltage dividing resistor 303, having a positive electric potential applied to the base through a resistor 300 for a resistor shunt. The collector of a transistor 400 forming part of the engine control unit (ECU) 4 is connected to the base of the transistor 320 through a lead wire A. The emitter of this transistor 400 is grounded, and an ECU signal is input to the base from various sensors.
Connected between the auxiliary output terminal 202 and the ground are voltage dividing resistors 304 and 305 for output voltage detection through a serially connected lead wire; a control transistor 321 whose emitter is connected to the ground and whose collector is connected to the auxiliary output terminal 202 through a resistor 306; and an output transistor 322, whose emitter is connected to the earth, whose base is connected to the collector of the control transistor 321, and whose collector is connected to the auxiliary output terminal 202 through a diode 313D. The ends of the field coil 102 are connected to the connection points among the auxiliary output terminal 202, the collector of an output transistor 322, and the anode of the diode 313D.
The anodes of diodes 310 and 311 are respectively connected to the connection points between the voltage dividing resistors 301 and 302 and the voltage dividing resistors 304 and 305. The cathodes of the diodes 310 and 311 are commonly connected to the base of the control transistor 321 through a Zener diode 312.
The operations of the conventional apparatus are described below by referring to the views showing the characteristics of the output voltage shown in FIG. 4.
If the key switch 8 is turned on when the engine is started, an electric current flows through the output transistor from the battery 5 through the key switch 8, the charge indication lamp 9, and the resistor 306. At this time, the battery voltage is not charged enough to set the Zener diode 312 in a continuity state. Therefore, the control transistor 321 remains in the OFF state.
When the output transistor 322 is turned on, an exciting current flows through the battery 5, the key switch 8, the charge indication lamp 9, the field coil 102, the output transistor 322, and the field coil 102 through the loop of the ground. At this time, the charge indication lamp 9 is turned on.
After the exciting current flows through the field coil 102 and the AC generator 1 is driven by the engine, the generated output is rectified by the rectifier 2 and output to the auxiliary output terminal 202, thereby raising the terminal voltage. When the terminal voltage of the auxiliary output terminal 202 equals or exceeds a predetermined value and becomes approximately equal to the battery voltage, the charge indication lamp 9 is turned off to indicate that the generating state is entered.
During the generating operation, if the charged voltage of the battery 5 is detected by the voltage dividing resistors 301, 302, and 303 from the charge detection terminal through the lead wire C, and if the charged voltage equals or exceeds a predetermined value (14.5V or 12.5V) described later, then the Zener diode 312 is set in a continuity state and the control transistor 321 is turned on.
When the control transistor 321 is turned on, the electric potential of the base of the output transistor 322 falls down to the electric potential of the ground, and the output transistor 322 is turned off with the exciting current reduced. As a result, if the output voltage drops, and the charged voltage of the battery 5 becomes lower than a predetermined value, then the output transistor 322 is turned on, the exciting current increases, the output voltage rises, and the charged voltage of the battery 5 also increases. These operations are repeated to adjust the output voltage into a predetermined value.
Described below is the operation to be performed when the output voltage is adjusted into 14.5V. When the ECU signal to a transistor 400 forming part of an ECU 4 is set OFF and the transistor 400 is set in the OFF state, a base current flows in the transistor 320 through the resistor 300. When the transistor 320 is turned on and shunts the voltage dividing resistor 303, the voltage dividing resistor is a serially connected voltage dividing resistors 301 and 302. If the battery voltage becomes equal to or higher than 14.5 V in this resistance ratio, then the divided voltage obtained using the voltage dividing resistor reaches the voltage level at which the Zener diode can be set in the continuity state. With the control transistor 321 set ON and the output transistor 322 set OFF, the exciting current decreases and the output voltage drops, thereby lowering the charged voltage of the battery 5.
If the charged voltage is equal to or lower than 14.5V and the control transistor 321 is turned off again, then the output transistor 322 is turned on and the exciting current increases, thereby raising the output voltage. These operations are repeated to adjust the output voltage into 14.5V.
However, if the engine is in the idle state and the electric load is almost zero, and the battery voltage is set to 12.5V to attenuate the load of the engine for the AC generator 1, then the ECU signal is set ON and the transistor 400 is set ON. As a result, the electric potential of the base of the transistor 320 becomes the electric potential of the ground, and the voltage dividing resistor is a serially connected voltage dividing resistor 301, 302, and 303. If the battery voltage becomes equal to or higher than 12.5 V in this resistance ratio, then the divided voltage obtained using the voltage dividing resistor reaches the voltage level at which the Zener diode can be set in the continuity state. The subsequent operations are the same as in the case that the output voltage is adjusted into 14.5V.
Thus, the load of an engine can be attenuated in an idle state, etc. by switching an output voltage. Such a switching operation is performed as an effective measure to improve the fuel efficiency.
As described above, the conventional apparatus is controlled such that the output voltage of the AC generator can be set to 14.5V. Since the amount of the generated voltage is reduced by switching the adjusted voltage into 12.5V according to a signal from the ECU, the load of the engine can be attenuated, thereby improving the fuel efficiency. The battery, however, cannot be quickly charged.
Furthermore, since the battery voltage becomes equal to or lower than 10V when the engine is started, there has been the problem with the conventional technology that the generator is in a generation state even if the adjusted voltage is switched into 12.5V, thereby failing to cut the generation and improve the starting characteristics.
The present invention has been developed to solve the above described problem, and aims at providing an AC generator control apparatus for automobiles capable of quickly charging a voltage, collecting an energy when the car is decelerated, completely cutting the generation, and improving the starting characteristics by attenuating the torque load when the engine is started.
1. The present invention includes a car battery charged by the rectified output from an AC generator for automobiles; a voltage regulator circuit for intermittently controlling the exciting current flowing through the field coil of the AC generator and adjusting the generated output voltage into a set value; and a set signal output unit for outputting to the voltage regulator circuit an output voltage value set signal of the AC generator depending on the detection results of various operation states of automobiles. The voltage regulator circuit includes a set value switching means for switching and setting a value of an output voltage of the AC generator depending on the contents of the set signal input from the set signal output unit; an output voltage detection means for detecting the output voltage of the AC generator; and an exciting current control means for intermittently controlling the exciting current depending on the comparison result between the detected output voltage and the set value of the set output voltage of the AC generator.
2. In the AC generator control apparatus for automobiles according to the present invention, the set signal output unit sets a duty ratio of a signal depending on the detected state of the operation of an automobile, and outputs the set signal with duty ratio to the set value switch means, and the set value switch unit discriminates the duty ratio and switches and outputs the output voltage set value corresponding to the duty ratio.
3. In the AC generator control apparatus for automobiles according to the present invention, the set value switch means sets the output voltage set value to the fourth predetermined value lower than the battery voltage when the system is started, sets the output voltage set value to the first predetermined value higher than the battery voltage during the normal operation after the system has been started, sets the output voltage set value to the second predetermined value higher than the first predetermined value when the car is decelerated and the battery is quickly charged, preliminarily sets the output voltage set value to the third predetermined value between the first and the fourth predetermined value when the electric load is small and a large system drive torque is required, and switches and outputs the predetermined value corresponding to the duty ratio from the comparison result between the output voltage set value corresponding to the input duty ratio and each of the predetermined values.
4. The AC generator control apparatus for automobiles according to the present invention is set to 14.5V as the first predetermined value, 16.5V as the second predetermined value, 12.5V as the third predetermined value, and 5V as the fourth predetermined value.
5. The AC generator control apparatus for automobiles according to the present invention includes a set means switch means which discriminates a duty ratio, converts the voltage of the signal having the duty ratio into the output voltage set value, and compares the set value with each predetermined value.
6. The AC generator control apparatus for automobiles according to the present invention includes an exciting current control means which switches the resistor voltage division ratio based on the comparison result of the set value switch means, outputs the divided voltage as an output voltage set value depending on the resistor voltage division ratio, and intermittently controls the exciting current based on the comparison result between the output voltage detected by the output voltage detection means and the output voltage set value.